Electric clock system



June 5, 1945. o. H; DICKE ETAL.

I ELECTRIC CLOCK SYSTEM Original Filed Jan. 14, 1939 2 .Sheets-Sheet l .52 -35 pa es cuceEL um 1 E 4. nm

em mm nu q v mm m QQQQ we vacuum 28 8 =26 oo fio mm v tEm INVENTORS BOYHDic Re and RHDI'CRC @MW THEIR ATTO NEY" June 5, 1945. o. H. DICKE ETAL ELECTRIC CLOCK SYSTEM Original Filed Jan. 14, 1959 2 Sheets-Sheet 2 INVENTORS O.H.Di

BY M32 and RHDickc THEIR ATT RNEY nwm Patented June 5, 1945 UNITED STATES PATENT OFFICE ELECTRIC CLOCK SYSTEM Oscar H. Dicke and Robert H. Dicke,

Rochester, N. Y.

Continuation of application Serial No. 250,964,

January 14, 1939.

This application June 14,

1941, Serial No. 398,129

12 Claims.

This invention relates to clock systems include ence of alternating current, dominated or otherwise regulated by such alternating current, and is an improvement over the prior applications of O. H. Dicke, Ser. No. 365,584, filed May 23, 1929, now Patent No. 2,248,164, dated July 8, 1941; Ser. No. 441,109, filed April 2, 1930, now Patent No. 2,331,267, dated October 5, 1943; Ser. Nos. 729,079 and 729,080, filed June 5, 1934, now Patents Nos. 2,248,165 and 2,185,334, respectively, and dated July 8, 1941, and January 2, 1940, respectively; Ser. No. 239,538, filed November 8, 1938, now Patent No. 2,359,973, and Ser. No. 245,700, filed December 14, 1938, now Patent No. 2,313,466, dated March 9, 1943; and the prior application of R. H. Dicke, Ser. No. 39,146, filed September 4, 1985, now Patent No. 2,151,317,

dated March 21, 1939, and constitutes a continuation application of our co-pending application Ser. No. 250,964, filed January 14, 1939, which became abandoned on June 21, 1941.

In many former clock systems, including some systems wherein alternating current synchronous motors are employed for actuating the sec-.

ondary clocks cumbersome and expensive mechanism is employed. These systems usually include electrically controlled mechanisms such as relays and electric clutches for correcting such secondary clocks, as for instance, after a current cessation.

In accordance with the present invention it is proposed to so construct the clock systems that the secondary clocks, of which there may be a large number, are of rather simple and inexpensive construction. One object of the present invention is to so construct the secondary clocks that increased voltage or increased frequency, depending on the particular system used, will cause the secondary clock to operate at increased speed until it reaches a predetermined chronological condition. At this predetermined chrono sides inthe provision of masterclocks which will operatein 'sub-synchronism with the frequency of alternating current of'regulated frequency so long as current is available and which will keep 5 substantially correct time during a current ces sation.

More specifically one of these master clocks includes an oscillatory member which through suitable mechanism drives a time shaft and which includes a local source of energy and means for 1,5;pu1ses,v whether advancing or retarding phase shifts, cause said member to drive said time shaft to very accurately reflect the passing of time, and additionally includes alternating current controlled means for dominating said memher so as to operate in synchronism with such alternating current and so as to cause this memher to be operated at an amplitude above this predetermined value so that this alternating current controlled mean performs a double function of keeping the member in sub-synchronism and of keepin the local source of energy from being dissipated. In one specific embodiment of master clock the oscillation" of the oscillating member is kept at or above a predetermined amplitude by the intermittent dropping of a weight. In one specific form of these master clocks as illustrated it is proposed to dominate the oscillation of such oscillating member through the medium of a very Weak spring driven by a synchronous motor.

In addition to the foregoing objects, purposes and characteristic features of the present invention it is proposed to so construct the master clocks and clock systems that secondary clocks of very simple construction operated entirely by alternating current of regulated frequency indicate substantially the same time irrespective of temporary current cessation and wherein the secondary clocks include no apparatus in addition to a synchronous motor and a clock train except contacts manifesting chronological conditions or blocking means to at times physically block operation of such secondary clock.

It is also proposed in accordance with the present invention to correct secondary clocks through the medium of contacts associated with the master clock and contacts associated with the secondary clock so that the secondary clock will operate at an average speed dependent upon the and non-correspondence of contacts associated.

with the master clock and the secondary clock.

Fig. 3 illustrates how the master clock of Fig. 2 may be modified to cause a supplemental correction to be made upon all secondary clocks during the last minute of each hour; and.

Fig. 4 illustrates how two frequencies instead. of two voltages may be used in the clock system illustrated in Fig. 2.

Fig. 1 structure Referring to Fig. 1, the structure shown therein is of two parts, namely, a master control clock and one or more secondary clocks of: which only one is shown.

Both the secondary and master clocks utilize a two-speed, self-starting, synchronous motor so designed as to operate at one synchronous speed for low voltage or low frequency excitation and.

at a higher synchronous speed for high voltage or high frequency excitation. The motors are utilized in the following way. During a power failure the secondary clocks are not operating, so immediately after a power failure high voltage is fed to the secondary clocks for the right length of time to bring them up by the amount which was lost during the power failure. Also each secondary clock is corrected once an' hour. This is accomplished by supplying high. voltage. to the clocks for the last minute or other suitable time interval ina way which will be described in more detail in the following paragraphs.

Referring now to Fig. l the secondary clock comprises a two-speed self-starting. synchronous motor SM to be described in more detail later.

The synchronous motor 8M through pinion I and gear train 38, 39, 40 and 4| drives the hour shaft 3 through gear 2. Clock: hands 4 are actuated by shaft 3. The cam K supporting pin 1 is rigidly connected to shaft 3. The cam lever 8 is pivoted on pin 9 and supports arm II, which in the upper position blocks pin. 1 and stopsrotation of cam K The cam lever 8 is latched up by the latch lever l2 pivoted at l3 and operated by anvil [2 The latch lever I2 is actuated by the armature l4 pivoted at l5. The armature i4 is biased to the upward position by the spring l1 and is actuated by the extended pole pieces I8 built out on the stator of the motor SM;

Referring now to the master clock correcting means in Fig. 1, this is composed of two parts; the master clock proper and the auxiliary mechanism for utilizing the master clock to regulate or correct the secondary clocks. The master clock proper is of a type which keeps time in accordance with the frequency of the regulated A; C. power supply so long as power is on the power line and which operates to indicate substantially correct time under its own power as'a mechanical clock while power is off.

' starting synchronous motor SM.

Referring now to the master clock portion of Fig. 1. Pendulum 2D with a heavy bob 2| is supported at pivot 22. Bumper I9 is so positioned as to restrict the amplitude of pendulum 20. Pendulum 20 is actuated by spring 23 supported or hooked on eccentric pin 24. Eccentric pin 24 is supported on gear wheel 26 which is driven through gear train 42, 43 and 45 by self-starting synchronous motor SM This gear train drives gear 26 at the same speed as the natural frequency of pendulum 20. The pendulum 20 carries a side arm 21 which is best shown in the enlargement in Fig. 1A. This side arm 2'! supports on pin 34 a flipper 29 which is freely pivoted thereon and has its center of gravity below the pin. Injuxtaposition to the flipper 29 is a trigger or pin 3| with a notch 32, being kept in normal position by pin 33. When pin 3| is raised due to the engagement of flipper 29 in notch 32 it actuates latch lever 35 pivoted on pin 36. Latch lever 35 latches armature 3'! in the upper position.

Referring again to Fig. l the armature 31 is pivoted on pin 46 and carries a contact member 48 which when the armature 31 is in the lower position makes contact completing the circuit from the battery BA through the electro-magnet MG causing the armature 3'! to jump again into the latched uppermost position. The armature 31 carries a roller 49 which in dropping rides on side arm 21 of the pendulum 20.

The remainder of the master clock proper consists of a clock gear train and a ratchet mechanism. Pin 59 carries an actuating lever 53 actuated by pendulum 20 through spring 5| and is used for actuating pawl 55. Limit pins 52 limit the-stroke of lever 53. Lever 53 carries a ratchet pawl 55 which actuates ratchet wheel 51 with the aid of the stationary pawl 53 which prevents retrograde motion of the ratchet wheel during retrograde movement of pawl 55'.

' ries contacts 63 and 55 the leads of which are taken of! by slip ring 65 and 61. In juxtaposition to these contacts 63 and 65 is the crank 10 carried on shaft 10 and so positioned as to engage the contact 65 which is longer than the con- 50' tact 63, and thereby opens the contacts 63 and 65. The shaft 10 in alignment with shaft 64 carries insulated cams K and K which actuate contacts 13-14 and 15l6. Shaft 10 is driven through gears 18 and by the two-speed self- Relays R and R and transformer T are employed tocontrol and energize suitable circuits as more particularly described hereinafter.

Fig. 1 operation During normal operation the secondary clocks as above described run as ordinary A. C. selfstarting synchronous motor clocks deriving their power from the controlled frequency A C. power lines except that during the last minute of every hour high voltage is supplied to these clocks causing their two-speed motors to run at the higher speed and thereby correct for any slight errors in their time indicating positions. In case of power failure the secondary clocks stop, but immediately after such power failure is terminated high voltage is supplied to the secondary clocks for such a period of time as is necessary to cause them to again indicate correct time.

Referring againto the secondaryv clock portion of Fig. 1, the operation is as follows. The twospeed synchronous motor SM through gear train I, 38, 39, 40, 4| and 2 drives clock hands 4 and cam K on minute shaft 3. The pin 1 which preferably carries a roller, is so positioned on the cam K as to strike the end of the arm H at the even hour position, providin the arm II is in the latched up position. The arm H is so positioned that the resultant torque about the point 9 is substantially zero. The cam K is so positioned on shaft 3 that cam lever 8 is freed there from immediately, say within one minute, before the even hour position. The normal operation then is as described in the following paragraph.

Let us assume that the time as indicated on the master clock is 58 minutes after the hour and that there has been no power failure during this hour, the two-speed self-starting synchronous motor SM is therefore energized through the medium of the clock system distribution lines a, I) through the following circuit: starting at the mid-tap of transformer T through back contact 85 of relay R front contact 8| of relay R contacts 1116 operated by cam K over line a through winding of synchronous motor SM to line b through common return wire C back to transformer T Now when the master clock indicates the 59th minute of the hour position the snap action contacts 161T open and the snap action contacts 15-16 close. This action is so rapid that there is no appreciable break in power supplied to the motor SM and the armature I 4 is not released. The circuit is now through contacts 'l5'l6 and contact 82 of relay R to the high voltage tap H of the transformer T This causes the motor SM to operate at its high speed, which is preferably three times normal speed, until pin 1 engages the end of arm ll stalling the motor 8M Now at the even hour position of the master clock the contacts 13|4 and 'l516 open and the contacts 1611 reclose. The opening of contacts 1314 causes the relay R which is energized through these contacts 13-14, to drop, opening the circuit to the motor SM for about one second. This releases the armature 14 of the motor SM causing it to strike the arm 12 of the latch lever I2, unlatching arm 8 and in turn the arm H and releasing pin 1. The contacts 'I3|4 close after about one second which causes picking up of relay R causing the system to resume normal operation. The secondary clock thus starts from the zero position of the hour when the master clock assumes the zero minute position. As shown the motor SM has a high synchronous speed which is three times its low synchronous Speed. Thus in one correction extending through a minute operation of the master clock it can correct a loss of two minutes.

In case of power failure the master clock keeps operating in a manner to be described later, but the remainder of the system is stationary. Thus, shaft is stationary but the minute shaft 64 of the master clock keeps'rotating. This causes contacts 6365 to close.

Upon resumption of alternating current power relay R is energized through contacts 13-14 and contacts 63-65 in series. This picking up of relay R opens back contact 85 and closes front contact 84 of relay R This causesthe high voltage to be fed to the motors SM and SM from high voltage tap H through the contacts 82 and 84 in series, instead of low voltage being fed through back contact 85. This causes the motors SM and SM to run at their high synchronous speed. Thus shaft 10 catches up with shaft 64, so

to speak and causing opening of contact 63-45 and causing the system to resume normal operation. Since the motors 8M and SM are similar and operate at the same speed for like voltages the secondary clocks will again indicate correct time.

However, there is a possible difliculty in a power outage correction that extends through the even hour position. Provision must be made for unlatching the arm 8 so as to allow the secondary clock to run through the even hour position during a correction resulting from power failure and being made through front contact 84 of relay RI and contacts 16-" controlled by cam K Let us now assume that a current cessation occurs at the fifty-five minute position of both the master clock and the secondary clock and that this current cessation continues for ten minutes. The master clock hands will then, upon termination of the current cessation, assume the five minute position, whereas the secondary clock shaft 3 and-the follower or catch-up shaft 10 will still be assuming the 55 minute position. Since the contacts 6365 have now been closed, because, the shaft 10 is tardy with respect to shaft 64, the relays R and R. both assume their attracted position upon the return of alternating current. For reasons above given the synchronous motors SM and SM are both operated at high speed (triple speed) so that the secondary clock .8 and the shaft 10 are both catching up with the master clock, so to speak. After 1% minutes of operation of the master clock the shaft 10 and the secondary clock hour shaft 3 assume the 60 minute position, in which position of shaft 3 and cam K the arm 8 is latched up. At the 60 minute position of the master clock shaft 10 the contacts 13-44 openresulting in deenergization of the relay R and R Dropping of the relay R results in reducing the voltage applied to the synchronous motor SM from high voltage to normal voltage resulting in normal speed operation of .the rewind motor 8M Dropping of the relay R results in opening of contacts 8| and 82 and in opening of both of the circuits for feeding energy to the line wire a, and results in deenergization of the secondary clock motor SM Deenergization of synchronous motor 5M causes it to release its tractive armature I4, causing it to strike the arm [2 and release the latch l2, thereby causing the end of arm H to disengage the roller or pin 1, allowing the secondary clock to operate freely. This deenergization of relay R continues only for about one second but long enoughto cause the tractive armature M to release, If desired suitable dash-pot or other means may be employed to make the armature l4 slow releasing. The secondary clock S is tardy only one second with respect to the shaft 10 which tardiness is due to the fact that the circuit for motor SM was open for one second during which time the motor 8M was energized at low voltage. When the master clock hand 62 assumes the ten minute position the shaft 10 will also assume the ten minute position, thereby causing the contacts 63-65 to open and causing the relay R to drop to its normal deenergized position. This removes high voltage from the motor SM and from the motor SM of the secondary clock thereby causing the secondary clock, now one second slow, to resume operation at normal speed. At the end of the next hour this one second error of the secondary clock S will of course be corrected in'a manner as already described. It is thus seen that the secondary clochSi-iscorrected afterv each current. cessation; and i also; corrected after each of a plurality of equal. time periods such.as anhour. It is desiredto point out: here that, if desired, the'synchronousamotors SM and SM of Fig. 1 may be of any suitable construction so long as they are self-starting and will operate at double: speed if double frequency'currentwof suitable voltage is applied thereto; In other words, the transformer. T may 'be. replaced; by the transformer 'I" and the frequencydoubler EDof Fig. 4' in the event such asynchronousmotor'is used and the Fig. l'system'is to bemodifiedfrom a two voltage system to atwoifrequencysystem. The operation of the master clock Mc under normal conditions andzduringa. currentcessation will now be described.

Operation of master clock Fig. 1

The operation of the master clock portion of Fig. 1, namely, the elements having". reference numbers to 64', can be conveniently considered under two separate headings, firstly normal operation, and secondly operation during power failure. We will first consider the-normal operation. The synchronous motorySM through gear. train 42-45-drives gear wheel 2E supporting eccentric pin 24. This sinusoidal motion of pin 24 through springv 23, which is always under tension, impresses a sinusoidal force onthe pendulum 20. As is shown in the theory of mechanics, this causes a vibration having the same period as the impressed force to be set up inthe pendulum 20. The strength of the spring 23:.isi soadjusted that the amplitude of the resultantzvibration is so great for ordinary variation in frequency. that the flipper 29 (Fig. 1A) completely clears the latch pin 3| on the swing to the left sothat on the return. swing to the right the flipper does not catch in the notch 32 (see Fig. 1A) Thus under normal operation the armature 31 remains in the latched up position and the battery BA is not used. The bumper. I9, althoughnot essential, is preferably used for reasons given below. practice the strength of thespring 23 is so adjusted as to cause the amplitude ofthe pendulum 20 to be great enough to strike the bumper l8 having a rubber impactor. W. This effectively limits the amplitude of the pendulum 20 and not only protects the clock. from damage due to too great an. amplitude but which also enables the clock to operate over a greater variation infrequency of thealternating current.

Coming now. to the second. phase of the opera-- tion of the master clock. in case ofipower failure the synchronous motor SM stops and the spring 23:110 longer'exertsthe above mentioned sinusoidal force. The pendulum now operates as an ordinary damped pendulumslowly decreasing in amplitude. The pendulumbob 2| is made very heavy so as to cause this decrease inv amplitude-to be very slow. When the amplitude of the pendulum 20 has decreased enough sothat onits swingto the left the flipper 29 does not completely clear latch pin 3| with the pendulumswinging to the right, the flipper 29 therefore catches in the notch 32 (see Fig. 1A) ofthe latch pin 3|, forcing it up and causing it to; operate latchlever 35 and so unlatch armature 31 and allow it tov drop toward the stop pin 30; This allows: the armature 31 to fall until the roller 49.: strikes the inclined member. 2! of the. pendulum. 20. 'Ihisexerts a force on. the pendulum in.a direction to increase its amplitude. The armaturefl continues to-fall until the contact fl'closescausing energization of magnet MGL which causes the armature to again jumpinto the latched-up position. The amplitude of the pendulum 20 is once more great enoughso that the dipper 29 clears latch pin II but is insufficient to strike the bumper l9, and the above process repeats itself each. time the amplitude has fallen sufiiciently to unlatch the armature 31. The clock is so designed that the impulse from the armature 3] acting on pendulum. 20 comes near the center of the swing of pendulum 20. This is done so that the impulse doesinot cause an appreciable shift in the phase of the pendulum. Whatever shift in phase there is however is compensated for by adjusting; the pendulum high or low depending on the direction of the phase shift.

We have examined the normal operation of the master clock pendulum, also operation during powerfailure, We now wish to briefly consider the synchronization of the pendulum in reverting to normal operation after a power failure. In general as the synchronous motor starts, neither the. phase nor thev amplitude of the pendulum is right for normal operation. This means that I there willexist a transient in the pendulum vibration andsince the pendulum 20 is so designed as to. have a low air resistance this transient would be a long time in being damped out. This difliculty is avoided in the following way. If the phase relation should be such as to cause the amplitude ofthe pendulum to fall, it falls until itunlatches armature 31. This gives the pendulum an impulse, and this impulse is such as;t0

help remove the transient vibration. If the amplitude increases, it does so until it strikes the bumper I9. Striking the bumper advances the phase and this continues until the phase has been advanced to such a point that the pendulum is in a condition of normal operation. Thus the bumper l9 acts as an upper limit and the apparatus 2'l |8 as a lower limit for the pendulum amplitude.

The pendulum 29. through the spring 5| actuates the lever 53 which in turn ratchets the ratchet. wheel 51 one tooth per cycle of the pendulum. The spring 5| is provided to enable the clock to operate for various amplitudes of the pendulum 20. The ratchet wheel 5'! through gear. train Git-8| drives the clock hands 62 and the shaft 64; The ratchet lever 53. is limited in its movement in opposite directions to an extent so that the ratchet pawl 55 pivoted to the ratchet lever 53 can advance the ratchet wheel. 5'! only one tooth for each left to right stroke of the ratchet lever 53. Also two fixed stop pins 56 provided one of which limits the. downward movement of ratchet pawl 55 and the-other of which causes binding action to prevent overthrow of the ratchet wheel 51. The spring 5| is of course stiff enough to transmit the force necessary to operate the master clock shaft. The fixed pawl 58 serves to prevent retrograde motion of the ratchet wheel 51.

Fig. 11? structure In Fig. 1B is illustrated a se1f-starting twospeed synchronous motor. It is of the type which employs magnetic hysteresis to produce retentitity of the steel rotor for synchronization. In particular, referring to Fig. 1B, is a laminated soft iron stator having pole pieces -426 and 9899. The reference character 8| designates an energizing windingthereon.

Copper. shading bands 93 and 94' divide thapole pieces into unshaded portions 95 and 99 and shaded portions 96 and 98. The air gaps I and IOI separate the poles 96 and 99, also 95 and 98. There are extensions 95, 96 98 and 99 on the pole pieces 9596 and 98-99. These extensions are preferably but a few laminations thick. The shaded and unshaded pole portions 95, 98 and 95, 88, respectively, are in quadrature with respect to each other and produce a two pole rotating field when the core structure is highly saturated. The pole extensions 95*, 96 98 and 99 bear the same angular relation to each other as do certain shaded and unshaded portions of the poles of a six pole machine, and these extensions alone carry a substantial amount of flux when low voltage is applied to the motor winding 9|. The rotor I03 of this two-speed motor is supported on shaft I04 and is stamped from a single lamination of hardened steel. Around the periphery of the rotor are six equally spaced slots I05, and in the central region are stamped two bilaterally symmetrical holes I06 as shown. These slots I and bilateral openings create two sets of preferential magnetic paths through the rotor and around the periphery. There are three such preferential magnetic paths formed by the slots I05 resulting in six residual magnetic poles when the motor operates at its low synchronous speed when energized at low voltage and there is formed one preferential magnetic path due to the holes I05 which results in a two pole residual magnetic structure when the rotor operates at the high synchronous speed due to the application of high voltage.

Fig. 1B operation The two synchronous speed operation of the motor illustrated in Fig. 1B depends upon the non-linearity of the permeability of the iron used in its construction. Under low voltage operation the pole extensions 95 96 98 and 99*: are the effective poles of the machine and the motor operates as a six pole machine. However, for high voltage excitation these pole extensions, which are reduced thickness, become saturated and the whole pole 95-96 also 98--99 becomes effective and the motor operates as a two pole machine. Let us consider first the low voltage operation.

' Referring to Fig. 1B for low voltage excitation we have the following operation. The pole extensions 95 96 08 and 99 can be regarded as forming a six pole stator in which some of the poles are omitted. to operate as a six pole synchronous motor of the ferrous hysteresis type. The slots I05 divide the rotor I03 into six pole pieces. After synchronous speed has been reached these poles take on a permanent magnetization. The direction of magnetization alternate for consecutive poles of the six poles of the rotor.

For high voltage excitation the pole extensions 95, 96 98 and 99 become saturated and the whole of poles 9596 and 9899 becomes effective. Under these conditions the stator is two pole and produces a two pole rotating field. This two pole field now has a synchronous speed of three times that of the six pole field and the motor operates at a synchronous speed of 3600 R. P. M. for (ii) cycle excitation instead of operating at 1200 R. P. M. The oblong holes I06 leave a magnetic path of low magnetic reluctance in one direction through the rotor I03 and this serves to lock the rotor in at high syn- This causes the motor chronous speed and thereby eliminates the slow slip which is otherwise present.

It is thus seen that in the master clock illustrated in Fig. l the alternating current not only functions to dominate the pendulum but it also serves as a cut-out device to cut-out the local source of energy, in the form of a battery, so that no power-off relay such as would ordinarily be used is required.

Fig. 2 structure In Fig. 2 is illustrated a modified clock system employing secondary clocks each including a synchronous motor which will operate at high speed or at low speed in accordance with whether the alternating current voltage is high or low, respectively, these motors being such as employed in Fig. 1 and illustrated on an enlarged scale in Fig. 1B. In this system the secondary clocks are at times held in a predetermined chronological condition by the opening of contacts rather than by being physically blocked at predetermined chronological conditions as is the case in the system of Fig. I. Also the system of Fig. 2 operates on the principle that if I suitable contacts of the master clock and similar contacts of the secondary clock are'not in correspondence the secondary clock will either operate at increased speed or will be held at stop, depending upon which of these contacts is leading the other.

Referring to Fig. 2 the master clock may be of any suitable construction insofar as the operating means for the master hour shaft 250 is concerned, so long as it is a master clock do1ninated or regulated by alternating current of regulated frequency, so as to operate in sub-synchronism with such frequency. In other words, the shaft 250 is driven by a master clock such as shown in Fig. 1 of this application or as shown in any one of the prior applications above referred to.

This master clock shaft drives clock hands 25! nd 252 and also drives a double contact arm 253 and a single contact arm 254, and rotates preferably at a speed of one revolution per hour. This shaft has been illustrated in the sixty minute or zero minute position. In this zero minute position the double contact 253 moves from the contact sector B to the contact sector A and the contact arm 254 which did not touch either of the segments A or B during the last minute of the hour begins toengage the segment B The segments A and B are of equal arcuate length and are separated by an arc of six degrees equal to one minute of movement of the contact arms 253 and 254. In other words, the double contact arm 253 engages the segment A during the first thirty minutes of each hour and engages the segment B during the second thirty minutes of each hour; whereas the contact arm 254 engages the segment B between the zero minute and the 29 minute position of the master clock and engages the segment A between the thirty minute and the fifty-nine minute position of the master clock shaft 250. Also, the contact arm 253 is connected to the movable contact 256 of the relay R through the medium of the slip ring and brush 251-258, so that the contact arm 253 is connected to the high voltage tap H of the transformer T when the relay R is up and is connected to the low voltage tap L when the relay R is down. Similarly, the contact arm 254 is continuously connected to the high voltage tap H of the transformefT,"throughthe'medium of the slip ring 260' an'd'the brush 26i The shaft-250 also carries 'aninsulating block 263 to'which are secure'd'contacts 264 and 6265,

which contacts arebiased'into engagement with each other. 'I'hc'se'contacts are'connected in series'with the relay R and'the lower portion of the secondary winding 'ofthe transformer T through the medium of slip rings 266 and 26l and brushes 268 and 269.

In axial alignment with the master clock shaft .250 is a follower shaft 210 bent at one end to form a crank 210%, 'which'crankis of aradius to engage contact 264 butnotcontactdii. This shaft 270 is driven at a speed-of one revolution anhour by the synchronous motor SM when this motor is energized by alternating current of-low voltage derived-from the tap L of transformer I as it normally is with the relay R deenergized. The crank-210%as shown, normally holds the contacts 264265-open, and since the master clock-containing shaft 250 is dominated by alternating currentfromthesame source as controls the motor the shafts-250 and 210rotate atexactly the same speed, .and the contacts 264-265 remainwbarely openso long as no current cessationtakes place. .The shaft2l0 isdriven through the medium of agear train including gears 21 2, 213 and 2T4and pinions 215, 216 and211.

Referring now to the secondary clocks S of Fig. 2, two of which only have been. illustrated, each of these secondaryclocks includes a time shaft or hour shaft 280 and clock hands 21! driventhrough the medium of a geartrainincluding gear28l and pinion 282by the synchronousmotor SM The .hour .shaft 280 drives .a. contact arm 284, which contact-arm is inengagement with segment a during the first .thirty minutes of an hour and is in engagement with thesegmentbduringthe second thirtyminutes of each hour as manifested by the secondary clock. This contact arm 284 isconnected to the winding of .the synchronous motor'SM through the medium .of a slip ring 285 and a brush 286, the other terminal .of this winding being connected to the common return wire C The segm'entza of each secondary clock .8 is connected to the'segment "A of the master clock 'MC bynetwork 288, whereas segments b 'and'B are connected to-' getherby' network 289.

Operation Fig. 2

The electric-clock system illustrated in Fig. 2

.is one of the type which functions on.the princinism with the contact arm 253 of the master clock, because if it (contact'284) moves on segment a just before the contact arm 253 moves on segment A the synchronous motor SM 'o'f the secondary clock will be'deenergized and the secondary clock S 'will stopuntil contact'253 also engages segment A and if the contact arm 284 is "still on the segment'b when 'the contact arm'253 begins to engage segment A (the eontact "arm 254 engaging the segment B at this same time) the synchronous motor SM is energized over the high voltage circuitwhich may be traced as follows: beginning at the high voltage terminal H of the transformer T brush 26l slip -ring=260, contact arm "25'4,-segment B wire-289. segment b, contact arm 284, slip ring 285, brush 7 286, winding of the synchronous motor 5M common return wireC and back 'tothe secondary winding of the'transformer T Thishigh alternating current voltage, for reasons heretofore given, will cause .thismotor SM to operateat its 'highsynchronous speed, preferably triple normal synchronous speed, .thereby causing the. secondary clock tocatch up, so tospeak, with :the master clock at least solongas the contactarm 284 remains in engagementwith'the segment 22:. It is :thus seen that if a particular secondary clocks is slow possibly becauseit was temporarily disconnected, iandisislow less than a half hour two-thirds of the tardiness of such particular'secondary clock'will be corrected at the end 'of eachhalf hour 'asmanifested' by the secondary clock. -For instance,=if we assumeithat a secondary clock *S 'isTtardy'twenty-seven minutes, by reason of a temporary disconnection from the line, when the "masterelockzis at the zero minute position. This tardinness will be reduced to nine minutes duringthe first half hour,wi11 be reduced to three minutes during the second half hour, will be .reduced'to'one minute during the third half hour, will be'reduced to twenty seconds dur-' ing the fourthhalfhour, andso on following the samearithmeticai progression until the tardiness is' negligible. It isthusseen that any tardiness of secondary -clocks not in excess of twenty-nine minutes may becorrected by the out-of-synchrothe master clock hais-reached the same position '(secondaryclock correct) "atwhich time the secondary clock resumes normal speed "operation and'again indicates correct time. .This function- 'ing of the ystem is 'due to theifact'that thecontact am 254 of the master clock .MC 'does not engage either of the two segments A or B duringthe thirtiethand the sixtieth minute of each 'hour. The system 0f..'Fig f5 thus causes any secondary clock that is slow twenty-nine minutes or less or is fast one minute Jorfless to be corrected and this can be done irrespective of whether or not the'relay R nandits control motor 'SM f'are employed or omitted. .In'this'connection it should 'be understoodithat'the motors SM and SM are of acconstructionan'd function like the motor "shown in Fig. '1B of the drawings. It

.shouidalso beunderstood that the. shafts 250 and -280'may make :one' revolution in any other suitable -time period such as twohours, for instance.

iLet:.us.nowobserve what'functions the relay R when used, performs. Let us assume that a power failure'or. current cessation takes place'at the two" minute position'ofthemaster clock MC "and'ithe secondary clock S 'andthat this'current cessation continues :for say fifty-five minutes. The master clock will then assume the fifty-seven minutezposition whereas the secondary clock still assumesthe two minute position, the master clock being .operated from a local source of energy all in a manner as'explainedin connection with Fig. -1 and the 2 prior applications heretofore referred to. Thecranlcflil of course still assumes the two minute position for which reason the contacts "264-405 are in :their biased closed position. Upon'retum'o'f 'thetalternating current of regulated frequency the relay R assumes its ener gized position and applies high voltage instead of low voltage to the contact arm 253, so that both of the arms 253 and 254 apply high voltage to the segments A and/or B During the first two minutes of operation of the master clock MC high voltage is applied to both of the wires 288 and 289 and segments a and b, but during the third minute high voltage will only be applied to the wire 289 and segment b; This is the case because the contact 254 is in the gap between segments A and B during the sixtieth minute of the master clock. Since the contact arm 284 assumes the eight minute position the secondary clock will be held at stop during this sixtieth minute of operation of the master clock. During this minute the catch-up motor 8M was however operated at its high or triple speed through a circuit including front contact 256 of relay R and. therefore the secondary clocks are slow to an extent of three minutes with respect to the catch up shaft 210, which shaft now assumes the eleven minute position. During the next twenty-dour and one-half minutes of operation of the master clock MC the shaft 210 fully catches up with the shaft 250 and the contacts 264-265 reopen, thus dropping the relay R causing the voltage applied to the contact arm 253 to be reduced to low voltage and causing the secondary clocks to be operated at normal speed instead of triple speed. The sec ondary clocks S are still three minutes slow with respect to the master clock M as before and as above explained and this tardiness will be corrooted in a. manner and for reasons heretofore given.

Fig. 3 system copstructz'on'and operation The system of Fig. 3 is the same as the system of Fig. 2 either with the relay R employed or with this relay R omitted, except that the contactarm construction is modified and performs functions not performed by the system of Fig. 2. In Fig. 2 the contact arm 2153 is a double contact which spans the one minute gap between segments A and B whereas the corresponding contact'arm 253 of Fig. 3 is a single contact which does not engage either of the segments A or B during the thirtieth and the sixtieth minute of each hour. It will be seen however that during the sixtieth minute of each hour the contact arm 254 applies alternating currentof high voltage to the segment B and during the thirtieth minute applies alternating current of high voltage to segment A This construction causes a secondary clock which is tardy less than two minutes to be fully corrected during the last minute of an hour or during the thirtieth minute 'of an hour, as the case may be, depending on when such clock became tardy. This is a function not performed by the clock system of Fig, 2. Although the relay R has not been illustrated in Fig. 3 such a relay R may be used and if used performs the same functions as described in connection with Fig. 2.

Referring again to the contact arm construction of Fig. 3 the contact arm m. performs a slightly different secondary clock retarding function than does its corresponding contact 254 of Fig. 2. This contact arm 25% leaves a particular segment A or B one minute earlier than does the contact 254 of Fig. 2, so that a secondary clock that is fast any amount less than two minutes will be corrected. This change with respect to contact arm Z54. in construction also results in a loss of six minutes'instead of three minutes of a sec ondary clock with respect to the catch-up shaft 216 of the master clock at the end of each half hour as manifested by the master clock, because one of the segments A or B and the corresponding secondary clock segment a or b will be entirely disconnected from alternating current at the end of such half hour for a period of two minutes instead of one as is the case in the Fig. 2 construction.

Fig. 4 system construction and operation In Fig. 4 has been illustrated how the four systems described in connection with Figs. 2 and 8 may be further modified. In the prior app1i cations of O. H, Dicke, Ser. Nos. 239,538 and 245,700 above referred to, now Patents Nos. 2,359,973 and 2,313,466, respectively, have been disclosed several forms of frequency doublers for changing a sixty cycle frequency alternating current, for instance, to a 1.20 cycle frequency alternating current. Referring now to the system illustrated in Fig. 2 if a double fre quency either of the same voltage or of double voltage be substituted and supplied instead of the high voltage supplied in Fig. 2 ordinary synchronous motors could be substituted for the special synchronous motors 5M and 8M of Fig. 2, and the system of Fig. 2 so modified, as corn veniently illustrated in Fig. 4, would function exactly the same as the system illustrated in Fig. 2. This modified system has been illustrated in Fig. 4, by illustrating in Fig. 4 how the transformer T of Fig. 2, irrespective of whether the relay R is used or omitted, may be replaced by the transformer T and the frequency doubler Fl) to constitute a modified system in which low frequency and high frequency alternating cur rents are alternately, in half hour periods, applied to the line wires 288 and 289. In the same manner the transformer 'I of Fig. 3 may be replaced by the frequency doubler FD and transformer T of Fig. 4- to constitute two additional modified systems depending on Whether the relay R is or is not used in such modified system. Figs. 2, 3 and 4 thus illustrate eight modified forms of system shown rather completely in Fig. 2 of the drawings. The two-speed synchronous motor shown in Fig. 1B of the drawings is claimed in a divisional application.

The applicants have thus shown and described several forms of their invention including modifled forms of master clocks constituting elements of these electric clock systems, and it should be understood that the systems illustrated. have been 3 selected to aid in the description of the principles employed and some manners in which these principles may be applied in practicing the invention, and that the invention is not limited to the particular constructions illustrated. For instance, any suitable synchronous motor which will operate at a low synchronous speed when low voltage is applied thereto and which will operate at a higher synchronous speed when al ternating currentof 'the same frequency but higher voltage is applied thereto may be substituted for the synchronous motor illustrated enlarged in Fig. 1B. Also, the system oi. Fig. 1 may be modified'by employing ordinary selfstarting synchronous, motors which will operate at a speed depending on the frequency instead of employing the two-speed synchronous motors illustrated in Fig. 1 and by employing the two frequency power pack illustrated in Fig. 4 instead of the transformer T employed in Fig. 1. It should therefore be understood that the pres ent:invention isnotlimited to the specific constructions illustrated except as demanded by thescope of the following claims.

What we claim as new is:

1. In an electric clock system; the combination with a source of-alternating current; of a master clock including a shaft rotated to substantially correctly manifest the passing of time; a secondary clock including a time shaft, 2. gear train, and a synchronous motor for operating such time shaft through themedium of said gear train; a first source of alternating current and a second source of alternating current adjacent said-master clock, which-first source of current will operate said secondary clock through the medium of its synchronous motor so as to substantially correctly manifest the passing of time and which second source if applied to said synchronous motor will cause said secondary clock to operate at increased speed; two circuits connecting said master clock and said secondary clock; a contact associated with said secondary clock for alternately-connecting said synchronous motor to one and then the other of said circuits during operation of said secondary clock; a first contact operated by the shaft of said master clock for alternately connecting said first source to one and then the other of said circuits; and a second contact operated by the shaft of said master clock foralternately connecting said second source to the other and then to said one of said circuits.

2. In an electric clock system; the combination with a sourceof alternating current; of a master clock including a shaft rotated to substantially correctly manifest the passing of time; a secondary clock including a time shaft, a gear train, and a synchronous motor for operating such time shaft through the medium of said gear train; a first source of alternating current of low voltage and a secondvsource of alternating current of high voltage adjacentsaid master clock, which first source of current will operate said secondary clock through the medium of its synchronous motor so as to substantially correctly manifest the passingof time and which second source if applied to said synchronous motor will cause said secondary clock to operate at increased speed; two circuits connecting said master clock and said secondary clock; a contact associated with said secondary clock for alternately connecting said synchronous motor to one and then the other of said circuits during operation of said secondary clock; a first contact operated by the shaft of said master clock for alternately connecting said first source to one and then the other of said circuits;-and a second contact operated .by the shaft of said master clock for alternately connecting said second source to the other and then to said one of said circuits.

3. In an electric clock system; the combination with a source of alternating current; of a master clock including a shaft rotated to substantially correctly manifest the passing of time; a secondary clock including a time shaft, a gear train, and a synchronous motor for operating such time shaft through the medium of said gear train; a first source of alternating current of low frequency and a second source of alternating current of high frequency adjacent; said master clock, which first source of current will operate said secondary clock through the medium of its synchronous motor so as to substantially correctly manifest the passing of timeand which second source if applied to. said synchronous motor will cause said secondary clock to operate at increased speed; two circuits connecting saidmaster clock and said secondary clock; a contact associated with said secondary clock for alternately connecting said synchronous motor to one and then the other of said circuits during operation of said secondary clock; a first contact operated by the shaft ofsaid master clock for alternately connecting said first source to one and then the other of said circuits; and a second contact operated by the shaft of said master clock for alternately connecting said second source to the other and then to said one of said circuits.

4. In an electric clock system; the combination with a source of alternating current; of a master clockincluding a shaft rotated to substantially correctly manifest the passing of time; a secondary clock including a time shaft, a gear train, and a synchronous motor for operating such time shaft through the medium of said gear train; a first source of alternating current and a second source of alternating current adjacent said master clock, which first source of current will operate said secondary clock through the medium of its synchronous motor so as to substantially correctly manifest the passing of time and which second source if applied to said synchronous motor will cause said secondary clock to operate at increased speed; two circuits connecting said master clock and said secondary clock; a contact associated with said secondary clock for alternately connecting said synchronous motor to one and then the other of said circuits during operation of said secondary clock; a first contact operated by the shaft of said master clock for alternately connecting said first source to one and then the other of said circuits; 8. second contact operated by the shaft of said master clock for alternately connecting said second source to the other and then to said one of said circuits; said first and second contact including means for applying voltage from said second source to said one circuit while no current is applied to said other circuit.

5. In an electric clock system; the combination with a source of alternating current; of a master clock including a shaft rotated to substantially correctly manifest the passing of time; a secondary clock including a time shaft, a gear train, and a synchronous motor for operating such time shaft through the medium ofsaid gear train; a first source of alternating current and a second source of alternating current adjacent said master clock, which first source of current will operate said secondary clock through the medium ofits synchronous motor so as to substantially correctly manifest the passing of time and which second source if applied to said synchronous motor will cause said secondary clock to operate at increased speed; two circuits connecting said master clock and said secondary clock; a contact associated with said secondary clock for alternately connecting said synchronous mo- 0 tor to one and then the other of said circuits during operation of said secondary clock; a first contact operated by the shaft of said master clock for alternately connecting said first source to one and then the other of said circuits; a second contact operated by the shaft of said master clock for alternately connecting said second source to the other and then to said one of said circuits; and supplemental means controlled by said master clock for causing the application of current from said second sourceto both of said increased speed;

circuits for a total period of time proportional to the duration of such current cessation.

6. In an electric clock system; the combination with a source of alternating current; of a master clock including a shaft rotated to substantially correctly manifest the passing of time; a secondary clock including a time shaft, a gear train, and a synchronous motor for operating such time shaft through the medium of said gear train; a first source of alternating current of low voltage and a second source of alternating current of high voltage adjacent said master clock, which first source of current will operate said secondary clock through the medium of its synchronous motor so as to substantially correctly manifest the passing of time and which second source if applied to said synchronous motor will cause said secondary clock to operate at increased speed; two circuit connecting said master clock and said secondary clock; a contact associated with said secondary clock for alternately connecting said synchronous motor to one and then the other of said circuits during operation of said secondary clock; a first contact operated by the shaft of said master clock for alternately connecting said first source to one and then the other of said circuits; a second contact operated by the shaft of said master clock for alternately connecting said second source to the other and then to said one of said circuits; and supplemental means controlled by said master clock and by current from said sources of alternating current effective after each current cessation to cause said first contact to apply said second source instead of said first source alternately to said circuits for a total period of time proportional to the duration of such current cessation.

7. In an electric clock system; the combination with a source of alternating current; of a master clockincluding a shaft rotated to substantially correctly manifest the passing of time; a secondary clock including a time shaft, a' gear train, and a synchronous motor for operating such time shaft through the medium of said gear train; a first source of alternating current of low frequency and a second source of alternating current of high frequency adjacent said master clock, which first source of current will operate said secondary clock through the medium of its synchronous motor so as to substantially correctly manifest the passing of time and which second source if applied to said synchronous motor will cause said secondary clock to operate at two circuits connecting said master clock and said secondary clock; a contact associated with said secondary clock for alternately connecting said synchronous motor to one and then the other of said circuits during operation of said secondary clock; a first contact operated by the shaft of said master clock for alternately connecting said first source to oneand then the other of said circuits; a second contact operated by the shaft of said master clock for alternately connecting said second source to the other and then to. said one of said circuits; and supplemental means controlled by said master clock and by current from said sources of alternating current effective after each current cess-ation from said sources to cause said first contact to apply said second source instead of said first source alternately to said circuits for a total period of time proportional to the duration of such current cessation.

8. In an alternating current electric clock systend, the combination with a central location and a field location, a master clock shaft at said central location, a secondary clock shaft at said field location, means for driving said master clock iii shaft to correctly manifest the passing of time, a synchronous motor for driving said secondary clock shaft to substantially correctly manifest the passing of time, when energized by alternating current of one character, but to operate at a much higher speed when energized by alternating current of another character, two line circuits con necting said central location and said field location, contacts for connecting said synchronous motor in said line circuits alternately for substantially equal timeintervals as manifested by said secondary clock shaft, and contacts controlled by said master clock shaft for alternately energizing one of said circuits with alternating current of said one character and of said other character and for alternately energizing the other of said circuits with alternating currents of said other character and of said one character in a manner such that neither of said circuits is energizedby-currents of both characters for any appreciable time.

location, means for driving said master clock shaft to correctly manifest the passing of time, a synchronous motor for driving said secondary clock shaft to substantially correctly manifest the passing of time when energized by alternating current of one character, but to operate at a much higher speed when energized byalternating current of another character, two line circuits connecting said central location and said field location, contacts for connecting said synchronous motor in said line circuits alternately for substantially equal time intervals as manifested by said secondary clock shaft, and contacts controlled by said master clock shaft for alternately energizing one of said circuits with alternating current of said one character and of said other character and for alternately energizing the other of said circuits with alternating currents of said other character and of said one character in a manner such that current of said one character is at all times applied to at least one of said circuits and alternating current of said other character is not applied to either of said circuits for a short time near the end of each of said time periods.

10. In an alternating current electric clock systom, the combination with a central location and a field location, a master clock shaft at said central location, a secondary clock shaft at said field location, means for driving said master clock shaft to correctly manifest the passing of time, a synchronous motor for driving said secondary clock shaft to substantially correctly manifest the passing of time when energized by alternating current of one character, but to operate at a much higher speed when energized by alternating current of another f character, two line circuits connecting said cencuits with alternating current of said one char-v acter and of said other character for substantially equal time periods and for alternately energizing the other of said circuits with alternating currents of said other character and of said one character for substantially equal time periods in a manner such that if time is divided into equal time periods alternating current of said one character is applied to one of said circuits for a predetermined fraction of such period and then to the other of said circuits for said predetermined fraction of such period alternately with the time of application in each case ending at the end of such period, and alternating current of said other character is applied to the other of said circuits for said predetermined fraction of such period and then to said one circuit for said predetermined fraction of such period alternately with the time of application in'each case starting at the beginning of such period, whereby said secondary clock shaft if fast will be temporarily stopped near the end of such period and if slow will be operated at increased speed near the end of such period.

11. In an alternating current electric clock system, the combination with a central location and a field location, a master clock shaft at said central location, a secondary clock shaft at said field location, means for driving said master clock shaft to correctly manifest the passing of time, a

synchronous motor for driving said secondary clock shaft to substantially correctly manifest the passing of time when energized by alternating current of one character, but to operate at a much higher speed when energized by alternating current of another character, two line circuits connecting said central location and said field location, contacts for connecting said synchronous motor in said line circuits alternately for substantially equal time intervals as manifested by said secondary clock shaft, and contact mechanism controlled by the said master clock shaft for applying said current of one character and said current of said another character to each of said line circuits alternately in such manner that current of a particular character is applied alternately to one and then the other of said line circuits.

12. In an alternating current electric clock system, the combination with a central location and a field location, a master clock shaft at said central location, a secondary clock shaft at said field location, a source of alternating current of one character, means for driving said master clock shaft to correctly manifest the passing of time as determined by the frequency of alternating current from said source so long as available and to substantially correctly manifest the passing of time during a current cessation, a synchronous motor for driving said secondary clock shaft to substantially correctly manifest the passing of time when energized by alternating current of said one character, but to operate at a much higher speed when energized by alternating current of another character, two line circuits connecting said central location and said field location, contacts for connecting said synchronous motor in said line circuits alternately for substantially equal time intervals as manifested by said secondary clock shaft, and contact mechanism controlled by the said master clock shaft for applying said current of one character and said current of said another character to each of said line circuits alternately in such manner that current of a particular character is applied alternately to one and then the other of said line circuits.

oscaa H. DICKE. ROBERT H. mcxa. 

